Irinotecan, a water-soluble camptothecin derivative, exhibits excellent anticancer activity through inhibition of topoisomerase-1 enzyme. At present, irinotecan is an anticancer agent frequently used for colon cancer or rectal cancer (Marschner et al., 2015) and marketed as an intravenous infusion (Iyer et al., 2002). However, this drug includes many anticancer side effects of other general anticancer agents. Further, there are attempts to increase drug efficacy by sustained release of a drug via intramuscular injection of the toxic drug such as irinotecan, etc. encapsulated in a hydrogel (Xuan et al., 2010). This hydrogel formulation is a formulation greatly increasing bioavailability while sustaining the drug release. However, there is a concern about side effects of the drug, which are caused by very high blood concentrations due to initial burst effect whereby the drug is initially released at a high concentration. Further, there is a problem that when used for a long time, muscle tissues may be greatly damaged because of direct contact of the toxic drug with muscle tissues.
Accordingly, there is a need for a new formulation capable of sustaining the efficacy of the toxic irinotecan and improving initial burst effect of the drug and safety to body tissues at the same time.